The present invention relates to network interfacing and, more particularly, to a novel network transceiver that uses signal detect input (SDI) pins for controlling modes of operations.
A Local Area Network, or (LAN), is a communications systems that provides a connection among a number of independent computing stations within a small area, such as a single building or group of adjacent buildings. One type of network structure uses one or more repeaters in a star typology, with each repeater having several ports. A data packet received at one port is retransmitted to all other ports of the repeater. Each repeater, in turn, restores timing and amplitude degradation of data packets received at one port and retransmits the packets to all other ports.
Traditional Ethernet networks (10BASE-T) operate at 10 Mb/s Ethernet protocol, as described by IEEE Standard 802.3; the majority of Ethernet interfaces currently operate at this data rate. However, a newer Ethernet network, under IEEE standard 802.3 u, accomplishes the faster operation of 100 BASE-T systems, at 125 Mb/s using unshielded twisted pair (UTP) physical media. The 100 BASE-T standard defines operation over two pairs of category 5 UTP cable for a 100 BASE-TX device. The 100 BASE-FX device, covered by the 100 BASE-T standard, allows operation over dual fiber optic cabling.
Ethernet protocol provides for a Media Access Control (MAC), enabling network interface devices at each network node to share accesses to the network medium. A Media Independent Interface, or MII, connects the MAC to a physical layer (PHY) transceiver configured for a particular network medium, e.g., 10 BASE-T, 100 BASE-FX, or 100 BASE-TX. The physical layer transceiver is configured for converting the MII protocol signals output by the MAC into analog network signals, such as Multiple Layer Transition-3 (MLT-3) signals for 100 Mb/s Ethernet networks or Manchester-encoded signals for 10 Mb/s Ethernet networks.
As Ethernet Physical Medium Dependent (PMD) devices operating over different media types use different signaling schemes, a separate network transceiver should be provided to support operations over each network media type. However, it would be desirable to provide a transceiver compatible with various types of PMD devices such as 10 BASE-T, 100 BASE-TX and 100 BASE-FX.
The invention provides a novel method of operating a physical layer device in a local area network, such as one conforming to Ethernet protocol, to make a single physical layer device compatible with PMD devices operating over different network media types. The methodology involves monitoring signal detect input pins and based on their levels, automatically reconfiguring the physical layer device to support interface to a required PMD device.
Typically, two signal detect inputs (SDI) are arranged for receiving an SDI signal indicating whether data received from the PMD device is valid. For example, the SDI signal may be at Positive Emitter-Coupled Logic (PECL) levels. The SDI signal that exceeds a required threshold level indicates that the received data is valid. An SDI control circuit automatically configures the physical layer device so as to support the interface to the required PMD device.
Preferably, the physical layer device comprises first transmitting and receiving paths for supporting interface to a first PMD device operable with data signals in a first format and second transmitting and receiving paths for supporting interface to a second PMD device operable with data signals in a second format. For example, Multi-Layer Transition (MLT-3) transmitting and receiving paths may be provided to support interface to 100 BASE-TX PMD device, and PECL transmitting and receiving paths may be arranged to support 100 BASE-FX PMD devices.
In response to a first logic value at the SDI, the SDI control circuit switches the physical layer device into a first mode of operation, in which the first transmitting and receiving paths provide data exchange with the first PMD device.
In response to a second logic value at the SDI, the SDI control circuit switches the physical layer device into a second mode of operation, in which the second transmitting and receiving paths provide data exchange with the second PMD device. Also, the SDI control circuit may place the physical layer device into a diagnostic loopback mode in response to a third logic value at the SDI.
Various objects and features of the present invention will become more readily apparent of those skilled in the art from which the following description of a specific embodiment thereof, especially when taken in conjunction with the accompanying drawings.